Power supply system providing filament and anode voltages for an electron discharge device



Feb. 19, 1952 A H. BOERDIJK ET AL 2, 6, 07

POWER SUPPLY SYSTEM PROVIDING F ILAMENT AND ANODE VOLTAGES FOR AN ELECTRON DISCHARGE DEVICE Filed Oct. 18, 1946 FILTER E INVENTORS ARIE HENDRK BOERDIJK$ JOHANNES MARINUS LOD VICUS %-1SSEN AGENT Patented Feb. 19, 1952 POWER SUPPLY SYSTE MENT AND ANODE ELECTRON DISCHARGE DEVICE Arie Hendrik Bo rdiik and Joh nnes M ri Lodevicus Janssen, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn, as trustee Application October 18, 1946, Serial No. 704,144 .In he Netherlands August .5

Section 1, Public Law 69 0, August 8, 1946 "Patent expires August 4, 1965 4 Claims.

This invention relates to a cir uit arra ement for energizing the filaments of one or more grid-controlled discharge tubes having a directly heated filament, by means of a source of d re current, more particularly a source of directcurrent having a comparatively high internal resistance and a comparatively low voltage.

In small radio receiving sets, amplifiers or the like, it is desirable to use one and the same voltage supply both for energizing the filaments and for producing the direct voltages for the positive electrodes of the discharge tubes used. The last-mentioned direct voltages are usually obtainable by means of a small converter, for instance a vibrator -converter, connected to the supply, and the consumption of filament current can be kept low by using tubes having directly heated filaments that are directly fed by the supply. In this way a single source of direct current having a very small size, a low weight and a comparatively low power, for instance a cellophane accumulator or a flashlight battery would be suificient, but the control-grid bias of the tube or tubes requires the use of a separate supply. This is why it has hitherto been impossible to construct such a small receiver, amplifier and so on comprising a single built-in supply.

For the negative control-grid voltage use might be made of the voltage drop caused by the filament current through the filament, it is. true, by electrically connecting the control grid ofthe discharge tube to the negative end of the filament, but by this expedient a very high disturbing voltage originating from the vibrator-converter is at the same time introduced into the control-grid circuit of the tube in the receivers and amplifiers in question. Since this disturbing voltage usually exceeds the signal voltage satisfactory reception or amplification is out of the question.

According to the invention the said voltage drop is nevertheless used for the desired grid bias, but the said disturbance is entirely or for the greater P t el m nated by makin u e o a bridge arrangement, in which the filament and the load causing the disturbance are each interposed in one of the two diagonal branches of the bridge, the source of direct current being inserted in one of the side branches. Care is preferably taken that the side branches only contain ohmic a resis an s.-

In this respect it is still to be pointed out that the usual means r l minatin disturbanc s would not be satisfactory in the cas under view. Thus, for instance, an electric filter in the fila- M PROVIDING FILA- VOLTAGES FOR AN ment supply is of little effect due to the low resistance of the filament. Furthermore, the said control-grid cannot be connected to the middle of a resistance connected in parallel with the filament, because in this case the grid voltage is not sufficiently negative. The use of a filament having a high thermal capacity is equally of no avail, because the electron stream behaves as if it issues fro-m the centre of the filament, and in respect of this centre the control grid has a disturbing voltage amounting to half the disturbing voltage set up across the whole filament, this independently of the emission of the filament. As has already been stated, separate supplies for the grid bias or for feeding the vibrator-converter in these small receivers, amplifiers or the like do not enter into account due to lack of space and with a view to saving weight.

Bridge arrangements have already been proposed for suppressing interferences, it is true, but in these arrangements the direct current supply and the source of disturbing voltage are located in the same diagonal branch, whereas the filament is inserted in the other diagonal branch. To make the direct current traverse the filament the side branches must include im-pedances, more particularly capacities. Owing to this, interference suppression takes place only for a single disturbing frequency or for a very small range of disturbing frequencies. In the present circuit arrangement such interferenc suppression would practically be useless since, for instance, a vibrator-converter generate noise voltages over a very large range of frequencies. It is by dividmg the disturbing element, for instance the vibrator-converter and the supply according to the invention that interference transmission is obtained for all frequencies.

In order that the invention will be clearly understood and readily carried into effect it will now be described with reference to the accompanying drawing representing, by Way of example, one embodiment thereof.

The sole figure represents a circuit arrangement for energizing the filament of the discharge tube I. This tube has a directly heated filament and its control grid is electrically connected to t e n gative end of this filam nt. Owing to this, he control grid a quires a n gative bias, which substantially corresponds to half the voltage drop u d by the filament cu rent in the filam nt. If thi ne ative bias is to be increased ac t-her re s anc may b interposed in the filament supply lead between the filament and the junction of the control grid circuit and this leadh n providing such a resistance (not represented in the drawing) the available voltage of the supply and the prescribed filament voltage of tube I have, of course, to be taken into account. The

filament current is taken from a source of direct current 2 e. g. a flashlight battery or a cellophane accumulator i. e. a supply having a small size, a small weight and a comparatively low power. The internal resistance of the supply 2 is represented by a resistance 3. In series with the filament of the discharge tube I and with the supply 2 is connected aresistance 4, the series connection of a variable resistance 5 and a fixed resistance 6 being connected in parallel with the filament. Furthermore, the primary winding l of the voltage step-up transformer in a vibratorconverter in series with the vibrating armature contacts actuated thereby is connected, in series with resistance 5, to the supply 2. After rectifying and filtering by conventional means, the voltages for the positive electrodes of the discharge tube I can be taken from the secondary winding 8 of the transformer associated with this vibrator.

As clearly appears from the drawing, the primary winding '1, which constitutes a source of strong disturbances, and the filament of the tube 1 are each inserted in one of the diagonal branches of the bridge arrangement, the supply 2 being inserted in one of the side branches of the bridge. A suitable choice of the resistances 4 and 6 and adjustment of the resistance 5 permits complete interference suppression of tube 1 for all disturbing frequencies. In the present circuit arrangement even the disturbance which otherwise (viz. when the bridge arrangement is not used and the negative grid voltage is taken from an additional battery) might still occur because the emission of the filament is influenced by the disturbing voltage, is avoided since the disturbing voltage cannot penetrate further to the filament.

In a practical embodiment where, for instance, tube I forms part of a small portable radio receiver (so-called pocket receiver) the various parts of the arrangement may have the following values:

Rs: 0.10 R4: S2 Rs: 2 Q Rs=200 fl Tube I comprises a space charge grid. The anode voltage, the screen-grid voltage and the voltage of the space charge grid amount to 15. These voltages are produced by means of the vibrator. The total direct current supplied by the vibrator amounts to about 2 /2 ma., the filament taking ma. at 1.4 volt. The source of direct current is a battery 2.

The drawing illustrates the energizing arrangement for only one tube, but of course, the circuit arrangement may also be used, without the need for other means, for energizing a plurality of tubes from one and the same supply.

What we claim is:

1. In combination with an electrical system provided with an electron discharge tube having a directly heated filament, a grid electrode and at least one additional electrode, apparatus for supplying power to said system comprising a Wheatstone bridge having first and second diagonals, a low-voltage source of direct current interposed in one arm of said bridge, said filament being connected across the second diagonals 'of said bridge for energization by said source,

and a vibratory converter producing a high voltage for application to said additional electrode and including the primary of a transformer in series with a vibratory element, said serially connected primary and element being connected across the first diagonals of said bridge for energization of said converter by said source, said bridge being balanced whereby disturbances produced by said converter are decoupled from said filament.

2. The combination, as set forth in claim 1, wherein said source has a relatively high internal resistance and wherein said bridge includes means to effect balance thereof.

3. In combination with an electrical system provided with an electron discharge tube having a directly heated filament, a grid electrode and at least one additional electrode, and means electrically connecting said grid to one end of said filament, apparatus for supplying power to said system comprising a four arm bridge having first and second diagonals, one arm of said bridge being constituted by a low-voltage source having a relatively high internal resistance, another arm of said bridge being constituted by a variable resistor, said filament being connected across the second diagonals of said bridge for energization by'said source, a vibratory converter producing a high voltage for application to said additional electrode and including the primary of a transformer in series with a vibratory element, said serially connected primary and element being connected across the first diagonals of said bridge to eifect energization of said converter by said source, and means in said bridge to' effect balance thereof.

4. In combination with an electrical'syste provided with an electron discharge tube having a directly heated filament,- a grid electrode and at least one additional electrode and means electrically connecting said grid to one end of said filament, apparatus forsupplying power to said system comprising a four arm bridge having first and second diagonals, one arm of said bridge being constituted by a low-voltage source having a relatively high internal resistance, another arm of said bridge being constituted by a variable resistor and the remaining arms being constituted by fixed resistors, said filament being connected. across the second diagonals of said bridge for energization by said source, and a vibratory converter producing a high voltage for application to said additional electrode and including an input transformer having a primary winding in series with a vibratory element, said serially connected winding and element being connected across the first diagonals of said bridge.

ARIE HENDRIK BOERDIJK.

JOHANNES MARINUS LODEVICUS JANSSEN.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 954,619 Fleming Apr. 12, 1910 1,649,016 Buckley Nov. 15, 1927 1,672,916 Snell June 12, 1928 2,219,928 Kalmus Oct. 29, 1940 2,228,868 Briebrecher Jan. 14, 1941 

